of milwaukee



A. SIMON. ELECTROMAGNET.

APPLiC'ATlON FILED OCT. I, 19!]. RENEWED MAY 17, I919.

Patented Dec.16,191 9.

M a m/w UNITED STATES PATENT OFFICE.

ARTHUR SIMON, 0F MILWAUKEE, WISCONSIN, ASSIGNOR TO THE CUTLER-HAMMER MFG. (10., OF MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN.

ELECTROMAGNET.

Specification of Letters Patent.

Patented Dec. 16, 1919.

Application filed October 1, 1917, Serial No. 194,143. Renewed May 17, 1919. Serial No. 297,906.

To all whom. it may concern:

Be it known that I, ARTHUR SIMON, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee, and State of Wisconsin, have invented new and useful Improvements in Electromagnets, of

which the following is a specification.

This .invention relates to electromagnets.

It is particularly applicable to lock-out switches, although it may be useful in other fields.

Lock-out switches are designed to remain open when the current in their operating winding or windings is high and to close when the current is below a predetermined value. Such switches are particularly adapted for use in starting systems for elec tric motors since they maybe made to remain open to keep a resistance in circuit when the motor is subjected to an abnormal current, and to close to remove the resistance when the current decreases to a safe value.

Lock-out switches usually comprise a closingmagnet tending to actuate the switch arm to close the switch, and a holding magnet tending to prevent closing movement of the switch arm. The two magnets exert relatively different pulls for different current values so that for current values below a certain point the closing magnet will predominate and close the switch, but for current values above that point the holding magnet will predominate and hold the switch open. As the closing magnet predominates below a certain current value there is a possibility of the switch closing at the first rush of current even though the current eventually is high enough in value to hold the switch open,'because the current does not rise to its high value instantaneously but passes through the low values at which the switch will close.

Various means have been devised for preventing this undesirable closing of the switch when a current that is relatively high in value is first supplied to the switch, most of which means involve the use of a damping coil associated with the magnetic cir-. cuit of the closing magnet to produce a lag in the building up of the closing magnets strength.

One object of the invention is to provide an improved electromagnet wherein the operation of the armature is delayed upon the application of suddenly rising excess current.

Another object is to provide improved means for causing the switch to remain open when current at a relatively high value is first supplied to the switch.

Another object is to provide a lock-out switch in which the failure of the switch to close at first rush of high current is due to the inertia of the movable parts of the switch.

Other objects will appear as the specification proceeds.

The lnvention is illustrated in the accompanying drawing, in which Figure 1 is afront elevation of a lockout switch constructed in accordance with the invention, and

Fig. 2 is a vertical longitudinal section thereof.

The electromagnet comprises in general a switch arm or armature pivoted intermediate its ends. The closing magnet acts on one end of the switch arm in a direction to close the switch, and the holding magnet acts on the other end of the switch arm in a direction torestrain the switch from closing. The two magnets exert relatively different pulls for different current values so that the closing magnet predominates over the holding magnet for relatively low current values and closes the switch, and the holding magnet predominates over the closing magnet for relatively high current values and holds the switch'open; The switch arm is normally biased to open ,position. In the switch illustrated the necessary predominance of the two magnets is accomplished by providing them with independent magnetic circuits whose relative reluctance varies for different current values. The reluctance of the magnetic circuit of the closing magnet increases more rapidly than the reluctance of the magnetic circuit of the holdin magnet, so that the pull exerted by the hiding magnet increases much more rapidly than the pull exerted by the closing magnet. Thus, as the current through the magnets increases above a predetermined value, the pull exerted b the closing magnet rises comparatively llttle while, because of its relatively slowly increasing reluctance, the pull exerted by the holding magnet continues to rise rapidly. Above the predetermined current value the relative reluctance of the closing magnet has increased to such a degree that the pull of the holding magnet predominates over the pull exerted by switch arm is prevented from moving by weighting the same in such a manner as to increase its inertia without increasing or decreasing the pull required to close/the switch. The closing magnet must first overcome the inertia of the armature or switch arm, before the armature starts to move. During this interval of time the holding magnet reaches the point where it predominates and the closing magnet reaches the point where it will no longer predominate and hence before the inertia of the armature is overcome the magnets will reach that point in their magnetization beyond which there is no tendency for the switch to close.

The switch arm or armature is shown at 1. It carries a movable contact 2 which cooperates with the stationary contact 3. The closing magnet is shown at 4 and the holding, magnet at 5.

The switch arm 1 is pivoted intermediate its ends on a pin 6 which is carried by a frame 7 of magnetic material that forms part of the magnetic circuit of the magnet 4. The arm 1 carries a stop 8 which abuts against the under surface of the frame 7 and limits the opening movement of the switch arm.

The upper portion of the switch arm 1 carries the contact arm 9 with which the contact 2 is associated. The contact arm 9 I is fulcrumed at 10 on the switch arm-1 and is yieldingly urged toward the switch arm by a coil spring 11. The arrangement is such that the contact 2 is adapted to engage the stationary contact 3 before the switch arm seals with the core of the magnet 4. After the contacts 2 and 3 come into engagement further movement of the switch arm 1 will cause the spring 11-to be compressed. The contact 2 is thereby closed against the pressure of the spring 11 and is given sufficient movement after engagement of the contacts 2 and 3 to produce a wiping action.

The lower portion of the switch arm 1 carries an adjustable armature 12 which cooperates with the core of the holding magnet 5. The armature 12 is carried by a threaded pin 13 which passes through the switch arm. The armature 12 may be adjusted by turning the same as will be obvious from the drawing and may be locked in its adjusted position by the lock nut 14. The adjustment of the armature 12 varies the length of the air gap between the armature and the core of the magnet 5 and therefore varies the effectiveness of the holding ma et.

he switch arm 1, or movable armature, may be so constructed that its weight will be sufficient to provide the required inertia to cause the above mentioned time lag in the movement of the armature. Instead of constructing the armature itself in such a manner as to rovide the necessa inertia, additional weight may be adde to the armature. The necessary mass of material for providing the additional weight may be associated with the armature in any suitable manner provided care is taken not to materially increase or decrease the pull necessary to actuate the armature. The required mass of material for providing the additional weight may take the form of a frame 15 connected to the switch arm 1 and pivotally mounted upon the pin 6. The frame 15 in the present instance comprises a side member 16 located at each side of the switch arm 1 and a connecting member 17 at the lower end of the frame serving to connect together the two side members 16. The upper ends of the side members 16 overlap the extensions or ears 18 on the upper end of the switch arm and may be connected to these ears in any suitable way so that the switch arm and the frame 15 moves as a unit.

The frame 15 is so applied, and the mass of the frame 15 is so distributed that the weight added above the pivot pin 6 will substantially balance the weight added below said pivot pin. In the present instance the mass of both the switch arm 1 and the frame 15 is so distributed that the switch arm and frame will be normally biased to open position. In the drawing the armature and frame are shown in their closed position. As the frame 15 is roperly balanced about the pivot pin 6 t e Inertia of the armature will be increased but the-pull required to actuate the switch arm will be neither increased nor decreased. The normal operating characteristics of the switch without the weight are therefore not affected by the addition of the weight.

It will now be evident that when current'is first supplied to the operating windings of the switch, the switch will remain open if the current value is above the value at which the switch is set to close, in spite of the fact that before the current reaches this high value it passes through the low values at which the switch will close. This is due to the fact that before the closing magnet can actuate the switch arm it must been illustrated and described in connection with a switch having two windings which may be connected in series with each other or in any other Way. However, the invention is equally applicable to magnetic switches of other types.

What I claim is:

1. An electric switch having a movable armature, an electro-magnet tending to actuate the armature to close the switch for relatively low current values, a magnet tending to hold the armature against movement for relatively high current values, and means controlled by said armature to delay the response thereof to said electro-magnet.

2. An electric switch having a movable armature, an electro-magnet tending to actuate the armature to close the switch for relatively low current values and a magnet tending to hold the armature against movement for relatively high current values, said armature being weighted to delay the response thereof to said electro-magnet.

3. An electric switch having a movable armature, an electro-magnet tending to, actuat the armature to close the switch and means whereby the armature is prevented from moving when the current is relatively high and is permitted to close when the curmeans whereby said armature is prevented from moving when the current is relatively high and is permitted to move when the current falls to a predetermined value, said.

armature being weighted so as to increase its inertia but not increase or decrease the pull required to actuate the same.

5. An electric switch having a movable armature, an electro-magnet tending to actuate the armature to close the switch, and means whereby the armature is prevented from moving when the current is relatively high 'and is permitted to close when the current falls to a predetermined value, the inertia of said armature being sufiicient to cause a delay in the response of the armature to said electro-magnet.

6. An electromagnet having a movable armature, a magnet for acting on said armature to move the same in one direction, a second magnet acting on said armature to move the same in the other direction, said magnets exerting relatively difierent pulls for difierent current values so that the armature is moved for relatively low current values but is held against movement for relatively high current values, and means controlled by said armature to delay the response thereof upon the application of suddenly rising excess current.

In witness whereof, I have hereunto subscribed my name.

ARTHUR SIMON. 

